緩衝區錯誤 - 錯誤轉換結果java.lang.nul ...和JSON解析數據的錯誤org.json.JSONException

Question

我在android中建立一個應用程序來記錄工作人員的出勤記錄，應用程序讀取人員的代碼從QR碼和數據庫中的表格更新。

我有兩個問題：

緩衝錯誤-誤差變換結果java.lang.null.PointerException JSON分析器-錯誤解析數據org.json.JSONException：輸入AR字符0的結束

繼承人是在MainActivity

package com.example.asistenciai; 

import java.util.ArrayList; 
import java.util.List; 

import org.apache.http.NameValuePair; 
import org.apache.http.message.BasicNameValuePair; 
import org.json.JSONException; 
import org.json.JSONObject; 
import android.app.Activity; 
import android.app.ProgressDialog; 
import android.content.Intent; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.widget.Button; 
import android.view.View; 
import android.view.View.OnClickListener; 




public class MenuActivity extends Activity { 

// Progress Dialog 
private ProgressDialog pDialog; 

// JSON parser class 
JSONParser jsonParser = new JSONParser(); 

// single product url 
private static final String url_update_attendance = "http://10.0.2.2/android_connect/update_attendance.php"; 

// JSON Node names 
private static final String TAG_SUCCESS = "success"; 
private static final String TAG_COD = "cod"; 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_menu); 

    //1. LOCALIZAR CONTROLES 
    final Button btnRegistrar = (Button)findViewById(R.id.BtnRegistrar); 

    btnRegistrar.setOnClickListener(new OnClickListener(){ 
     @Override 
     public void onClick(View v) { 
       // TODO Auto-generated method stub 
      Intent intent = new Intent("com.google.zxing.client.android.SCAN"); 
       intent.putExtra("SCAN_MODE", "QR_CODE_MODE"); 
       startActivityForResult(intent, 0); 
     } 

     }); 

    } 

public void onActivityResult(int requestCode, int resultCode, Intent intent) { 
     if (requestCode == 0) { 
      if (resultCode == RESULT_OK) { 
      String contents = intent.getStringExtra("SCAN_RESULT"); 
      if(contents.equals("64572215")){ 
       new ActualizarAsistencia().execute(); 

       /*Intent i = new Intent(MenuActivity.this, ResultadoOkActivity.class); 
       startActivity(i);*/ 
      }else{ 
       Intent i = new Intent(MenuActivity.this, ResultadoFalloActivity.class); 
       startActivity(i); 
      } 
      } else if (resultCode == RESULT_CANCELED) { 
      // Handle cancel 
      } 
     } 
    } 

    class ActualizarAsistencia extends AsyncTask<String, String, String> { 

     /** 
     * Before starting background thread Show Progress Dialog 
     * */ 
     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      pDialog = new ProgressDialog(MenuActivity.this); 
      pDialog.setMessage("Saving attendance ..."); 
      pDialog.setIndeterminate(false); 
      pDialog.setCancelable(true); 
      pDialog.show(); 
     } 

     @Override 
     protected String doInBackground(String... args) { 

      //this is an example 
      String cod = "64572215"; 


      List<NameValuePair> params = new ArrayList<NameValuePair>(); 
      params.add(new BasicNameValuePair(TAG_COD, cod)); 

      JSONObject json = jsonParser.makeHttpRequest(url_update_attendance, 
        "POST", params); 

      // check json success tag 
      try { 
       int success = json.getInt(TAG_SUCCESS); 

       if (success == 1) { 
        // successfully updated 
        Intent i = getIntent(); 
        // send result code 100 to notify about product update 
        setResult(100, i); 
        finish(); 
       } else { 
        Intent i = new Intent(MenuActivity.this, ResultadoFalloActivity.class); 
        startActivity(i); 
       } 
      } catch (JSONException e) { 
       e.printStackTrace(); 
      } 

      return null; 
     } 

     /** 
     * After completing background task Dismiss the progress dialog 
     * **/ 
     protected void onPostExecute(String file_url) { 
      // dismiss the dialog once product uupdated 
      pDialog.dismiss(); 
     } 


    } 


} 

和這裏的JSONParser類

package com.example.asistenciai; 

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.io.UnsupportedEncodingException; 
import java.util.List; 

import org.apache.http.HttpEntity; 
import org.apache.http.HttpResponse; 
import org.apache.http.NameValuePair; 
import org.apache.http.client.ClientProtocolException; 
import org.apache.http.client.entity.UrlEncodedFormEntity; 
import org.apache.http.client.methods.HttpGet; 
import org.apache.http.client.methods.HttpPost; 
import org.apache.http.client.utils.URLEncodedUtils; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.json.JSONException; 
import org.json.JSONObject; 

import android.util.Log; 

public class JSONParser { 

static InputStream is = null; 
static JSONObject jObj = null; 
static String json = ""; 

// constructor 
public JSONParser() { 

} 

// function get json from url 
// by making HTTP POST or GET method 
public JSONObject makeHttpRequest(String url, String method, 
     List<NameValuePair> params) { 

    // Making HTTP request 
    try { 

     // check for request method 
     if(method == "POST"){ 
      // request method is POST 
      // defaultHttpClient 
      DefaultHttpClient httpClient = new DefaultHttpClient(); 
      HttpPost httpPost = new HttpPost(url); 
      httpPost.setEntity(new UrlEncodedFormEntity(params)); 

      HttpResponse httpResponse = httpClient.execute(httpPost); 
      HttpEntity httpEntity = httpResponse.getEntity(); 
      is = httpEntity.getContent(); 

     }else if(method == "GET"){ 
      // request method is GET 
      DefaultHttpClient httpClient = new DefaultHttpClient(); 
      String paramString = URLEncodedUtils.format(params, "utf-8"); 
      url += "?" + paramString; 
      HttpGet httpGet = new HttpGet(url); 

      HttpResponse httpResponse = httpClient.execute(httpGet); 
      HttpEntity httpEntity = httpResponse.getEntity(); 
      is = httpEntity.getContent(); 
     }   


    } catch (UnsupportedEncodingException e) { 
     e.printStackTrace(); 
    } catch (ClientProtocolException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 

    try { 
     BufferedReader reader = new BufferedReader(new InputStreamReader(
       is, "iso-8859-1"), 8); 
     StringBuilder sb = new StringBuilder(); 
     String line = null; 
     while ((line = reader.readLine()) != null) { 
      sb.append(line + "\n"); 
     } 
     is.close(); 
     json = sb.toString(); 
    } catch (Exception e) { 
     Log.e("Buffer Error", "Errore converting result " + e.toString()); 
    } 

    // try parse the string to a JSON object 
    try { 
     jObj = new JSONObject(json); 
    } catch (JSONException e) { 
     Log.e("JSON Parser", "Errore parsing data " + e.toString()); 
    } 

    // return JSON String 
    return jObj; 

} 
} 

的logcat的

05-31 18:08:28.325: E/Buffer Error(25370): Errore converting result java.lang.NullPointerException 
05-31 18:08:28.325: E/JSON Parser(25370): Errore parsing data org.json.JSONException: End of input at character 0 of 
05-31 18:08:28.360: E/AndroidRuntime(25370): FATAL EXCEPTION: AsyncTask #1 
05-31 18:08:28.360: E/AndroidRuntime(25370): java.lang.RuntimeException: An error occured while executing doInBackground() 
05-31 18:08:28.360: E/AndroidRuntime(25370): at android.os.AsyncTask$3.done(AsyncTask.java:299) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at java.util.concurrent.FutureTask.setException(FutureTask.java:124) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at java.util.concurrent.FutureTask.run(FutureTask.java:137) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at java.lang.Thread.run(Thread.java:856) 
05-31 18:08:28.360: E/AndroidRuntime(25370): Caused by: java.lang.NullPointerException 
05-31 18:08:28.360: E/AndroidRuntime(25370): at com.example.asistenciai.MenuActivity$ActualizarAsistencia.doInBackground(MenuActivity.java:109) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at com.example.asistenciai.MenuActivity$ActualizarAsistencia.doInBackground(MenuActivity.java:1) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at android.os.AsyncTask$2.call(AsyncTask.java:287) 
05-31 18:08:28.360: E/AndroidRuntime(25370): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 
05-31 18:08:28.360: E/AndroidRuntime(25370): ... 5 more 

感激，如果你能幫助我！

Answer 1

問題是您的json變量爲空。因此JSONParser的方法makeHttpRequests返回null。也許問題是下面幾行：

if(method == "POST") { 
    ... 
} else if (method == "GET") { 
    ... 
} 

你不能==比較字符串，但你應該使用equals()。就像這樣：

if(method.equals("POST")){ 
    ... 
} 

Answer 2

你寫，你得到的LogCat如下：

Buffer Error-Error converting result java.lang.null.PointerException JSON Parser-Error parsing data org.json.JSONException:

所以，錯誤的可能性是調用下面的語句時，你的is變量爲空：

BufferedReader reader = new BufferedReader(new InputStreamReader(
      is, "iso-8859-1"), 8); 

所以它返回一個空指針異常。因爲它是在try-catch塊中設置的，所以它是並顯示Buffer Error: ...，然後如json變量將爲空（因爲is爲空），所以現在當您嘗試解析對象時，jObj變量也會拋出一個例外。所以現在你也得到JSON parse error。

您必須確保is不爲空。 嘗試並把整個BufferReader的東西和解析的東西放在你設置is變量的值的同一個try-catch塊中。這可能是因爲你的BufferReader取空，你通過它初始化頂端的變量is。因此，儘量將它全部放在同一個try（）塊中。希望有所幫助。